Maintaining the Resistor Divider Ratio During Start-up
AssigneeDialog Semiconductor GmbH
InventorsAmbreesh Bhattad, Ludmil Nikolov, Marinus Wilhelmus Kruiskamp
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Abstract
Circuits and methods to maintain a resistive voltage divider ratio during start-up of an electronic circuit comprising a feed-forward capacitor across a feedback resistor using a dynamic start-up circuit are disclosed as e.g. a LDO or an amplifier. In a preferred embodiment of the disclosure is applied to an LDO. Modification of the resistive voltage divider ratio caused by the feed-forward capacitor during start-up is prevented while the voltage level of a voltage access point of the voltage divider on the feed-forward capacitor is maintained. Embodiments of the disclosure presented comprise using a start-up buffer or a start-up capacitor during the start-up phase.
Claims24
A method to maintain a resistive voltage divider ratio during start-up of any electronic circuit comprising a feed-forward capacitor across a feedback resistor of a resistive voltage divider using a dynamic start-up circuit, comprising the following steps:
- (1) providing an electronic circuit comprising a feed-forward capacitor across a first feedback resistor of a resistive voltage divider and a start-up circuit;
- (2) avoiding modification of resistive voltage divider ratio caused by feed-forward capacitor during start-up phase;
- (3) monitoring output voltage and finish start-up-phase when desired output voltage of the electronic circuit is reached;
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- (4) processing normal operation after start-up phase is finished wherein feed-forward capacitor is connected across the feedback resistor of the resistive voltage divider after end of start-up phase.
A circuit to maintain a resistive voltage divider ratio during start-up of any electronic circuit comprising a feed-forward capacitor across a feedback resistor and a resistive voltage divider using a dynamic start-up circuit, comprising:
- the feed-forward capacitor, wherein a first plate of the feed-forward capacitor is connected to an output port of the circuit and a second plate is connected to a voltage access point of the resistive voltage divider after the start-up phase of the electronic circuit is finished;
- said resistive voltage divider, being connected between an output port of the circuit and ground, comprising the feedback resistor having a resistance R2 connected between the output port of the circuit and the voltage access point in-between the voltage divider having a fraction of the output voltage and further comprising a second resistor having a resistance R1;
- a start-up comparator detecting if the start-up phase is finished by comparing a voltage representing the output voltage of the electronic circuit with a reference voltage;
- a means to maintain a voltage level of the voltage access point across the feed-forward capacitor during start-up of the circuit, wherein the means to maintain a voltage level of the voltage access point comprises switching means to connect or disconnect components of the circuit at beginning and end of the start-up process, wherein the switching means are activated by the start-up comparator.
Dependencies are inferred from the claim text.